1. Field of the Invention
The present invention relates to an image forming apparatus provided with a toner container for replenishing a developing device with toner particles and used as a copier, a facsimile machine, a printer or the like.
2. Description of the Related Art
An image forming apparatus of the electrophotography type includes a charger, an exposing device, a developing device, a transfer device, a cleaning device and the like arranged around a photoconductive drum. An electrostatic latent image is formed on the outer circumferential surface of the photoconductive drum uniformly charged by the charger by illuminating this circumferential surface with a light having image information from the exposing device. A toner image is formed on the outer circumferential surface of the photoconductive drum by supplying toner particles from the developing device and is transferred to a sheet. The sheet having the toner image transferred thereto is fixed by heating in a fixing device disposed downstream of the photoconductive drum and then discharged to the outside.
In such an image forming apparatus, toner particles needs to be replenished since toner particles filled in the developing device is consumed in the developing process. There are generally the following two methods for the toner replenishment.
According to a first method, a developing unit integrally provided with a toner container is employed as a developing device and is replaced by a new one having toner particles filled in a toner container when toner particles runs out (see, for example, Japanese Unexamined Patent Publication No. 2004-45960). Contrary to this, according to a second method, a toner container for supplying toner particles to a developing device is provided and only the toner container is replaced by a new one without replacing the developing device when toner particles runs out (see, for example, Japanese Unexamined Patent Publication No. 2002-278424).
The first method not only leads to a cost increase due to the need to replace the still usable developing device every time toner particles runs out, but also forces the developing device to have a large capacity because of the content of toner particles to deal with at least about 4000 sheets by one replacement, which is against the tendency to make the apparatus smaller in size. Contrary to this, the second method provides a lower cost because only the toner container is replaced and accordingly does not make it necessary to enlarge the capacity of the toner container much, thereby contributing to the downsizing of the apparatus just by that much.
According to the second method, as disclosed in Japanese Unexamined Patent Publication No. 2002-278424, the toner container mounted into an apparatus main body is retained in the apparatus main body by means of a locking member such as a lock spring or the like, and this retained state is canceled by pressing an unlocking member. The unlocking member is in the form of a button, and an operator presses this button-shaped unlocking member with his fingertip, thereby canceling the interlocked state of the toner container with the apparatus main body. However, there has been a problem that the pressing operation cannot be smoothly performed by being hindered by the fingernail of the operator, for example, if the fingernail is too long.